It is often necessary to vary, during operation, the emission direction of a light source whose light is bundled into a limited solid angle range, as in the case of floodlights, for example. This is of interest particularly in the case of automobile headlights in travel on curves, when the beam direction of the headlight is intended to track the particular direction of travel, as a so-called dynamic curve light. Such headlight systems have become known in particular from the Citroen DS series. Dating back much farther, however, there were rotary headlight mountings which were mechanically connected to the steering, causing the headlights to swivel along with the front wheels as the vehicle was steered.
With the advent of the use of light-emitting diodes (LEDs) in headlights, there was a resurgence of interest in dynamic curve light, now known as AFS (advanced front-lighting systems). AFSs are intended not only to provide better illumination of the road in the particular direction of travel on a curve, but also to adapt the particular light distribution to different environmental conditions.